Mobile wood chipping machines are used by workmen to chip branches and parts of trees into smaller pieces for providing mulch or to make the pieces of the tree more easily transportable to other locations or for easy disposal. Such machines have a feed chute leading into a chamber where chipping discs are present and the discs are driven to cause material introduced into the chamber to be shredded or chipped into small pieces. A pair of feed rollers is present at an end of the chute spaced from a feed opening into the chute. The feed rollers convey material placed into the chute towards the chipping discs. A safety bar extends across the chute in the vicinity of the feed opening. The bar is normally pulled away from the chute to cause a drive to rotate the feed rollers and is pushed towards the chute to disengage the drive.
Serious accidents have been known to occur with the use of such machines. It is usual for workmen to wear gloves and other protective clothing, and it is possible that material being fed into the chute may snare a workman. If a workman is snared by material being fed into the chute the workman may be unable to operate the safety bar in time or may be unable to operate the bar at all. As a consequence, the workman may be drawn into the machine and injured. Furthermore, the safety bar may malfunction.
Similar problems and accidents also occur with material processing machines such as presses and the like. Presses have an operative region in which, for example, sheets of material such as metal are pressed, bent or formed into a desired shape, often by a hydraulic system forcing a blade having shaped forming elements onto the material. The press also has an access region through which an operator passes the material to be pressed and retrieves the pressed material. Presses typically operate at between about 30 and 75 strokes per minute and if an operator becomes ensnared with the material being pressed and/or the machine parts, the rapid operation of the press may cause injury to the operator before the operator is able to free himself.
Another consideration is that workers of different qualification and experience levels may be involved with material processing machines and the like. For example, a technician may be qualified to maintain a machine, but not qualified to operate the machine. The converse may be true for an operator. Both would be permitted to work in proximity to the machine, but only the operator would be permitted to operate it. Accidents often occur when unqualified, or inappropriately qualified, workers operate such machinery. Furthermore, unknown to an operator, a technician may be working on a machine when the operator commences operation of the machine, possibly resulting in injury to or death of the technician.
It is an object of the present invention to provide a safety system for machinery that overcomes, or at least ameliorates, one or more of the deficiencies of the prior art.